A large-scale deletion of friends from a social networking site. Similar to deforestation, it can have drastic effects on the remaining landscape of your friends list. The people you unfriend may then Facebook chat rape or Facebook stalk your mutual friends, asking why you've cleared an entire forest of people.
"I had to do some serious defriendization on FB after I dumped my stupid ho. No big deal, I hate her skanky, retarded friends anyway. Sorry if they come after you asking what happened, just tell them to get stuffed."